The present invention relates to a wireless communication apparatus, and particularly to a wireless communication apparatus that can be reduced in size and improve antenna characteristics.
Conventionally, in miniaturizing a wireless communication apparatus, a radio-frequency wireless communication circuit (RF circuit) and an antenna are miniaturized separately from each other. When the RF circuit and the antenna circuit are miniaturized separately from each other, however, there is a limit to miniaturization of the wireless communication apparatus as a whole.
Accordingly, in general, attempts have been made to miniaturize the wireless communication apparatus as a whole by integrating a module and a semiconductor used in the wireless communication circuit with the antenna (see for example patent literature 1, patent literature 2, patent literature 3, and patent literature 4).
In a receiving module unit described in the patent literature 1, an antenna and a circuit protected with a shield pattern for magnetic shielding are formed on an identical plane, whereby the receiving module as a whole is miniaturized and mutual effects between the circuits are eliminated.
In a semiconductor package described in the patent literature 2, an antenna pattern in a shape of one loop is provided around an IC chip on a circuit board, thereby effecting miniaturization.
In an antenna module and a wireless communication apparatus using the antenna module described in the patent literature 3, an antenna is laminated on a circuit board via a dielectric substrate, and a layout of internal parts is optimized to avoid effects on a portion that greatly contributes to frequency bandwidth in the antenna device, thereby effecting miniaturization.
In the case of an antenna built in a computer terminal described in the patent literature 4, which antenna is not integrated with a wireless communication circuit, a slot antenna is formed using a thin plate-shaped stay, and the slot antenna is installed in a gap at a sidewall of a computer frame, thereby effecting miniaturization.
[Patent Literature 1]
Japanese Patent Laid-Open No. Hei 9-116240 (page 3, FIG. 1)
[Patent Literature 2]
Japanese Patent Laid-Open No. Hei 7-176646 (page 2 and page 3, FIG. 1)
[Patent Literature 3]
Japanese Patent Laid-Open No. 2001-298321 (page 3 and page 4, FIG. 1)
[Patent Literature 4]
Japanese Patent Laid-Open No. 2002-84117 (page 5 and page 6, FIG. 2 and FIG. 5)
However, the receiving module unit in the patent literature 1 and the semiconductor package in the patent literature 2 have problems in that when a ground pattern of the board is adjacent to the antenna pattern, antenna efficiency is degraded significantly and, at the same time, a narrower band results.
As to the antenna module and the wireless communication apparatus in the patent literature 3, it is known regarding frequency bandwidth and antenna efficiency of a line-shaped antenna and a plate-shaped antenna that characteristics including radiation resistance, a frequency band and the like are generally determined in proportion to a square of a distance from a ground of the board to the antenna device. Depending on required specifications, sufficient miniaturization is difficult in some cases with these structures.
The antenna built in the computer terminal in the patent literature 4 is a slot antenna. However, this slot antenna requires a ground plate that is sufficiently wide with respect to the wavelength. In addition, to avoid electromagnetic coupling with the wireless communication circuit, the antenna is installed at a distance from the wireless communication circuit or the antenna and the wireless communication circuit are used on respective boards separate from each other in many cases, thus making miniaturization difficult.